This invention relates generally to novel organic copolymers and methods of use thereof, and more particularly, to novel phosphonate copolymers with alternating functional groups and their use in metal chelation and in forming multilayer structures.
The design and synthesis of thin films and chemically modified surfaces has been an area of intense research activity because of the potential utility of these structures. Various applications including optical second harmonic generation, (Katz, H. E. et al., J. Am. Chem. Soc. 112:7389 (1990)) chemical sensing (Kepley, L. J. et al., Anal. Chem. 64:3191 (1992)), electrical or environmental isolation (Swalen, J. P. et al., Langmuir 3:932 (1987)), electronic rectification (Metzger, R. M. et al., Langmuir 6:350 (1990)), and photoreactivity (Dulcey, C. S. et al., Science 252:551 (1991); Calvert, J. M. et al., Thin Solid Films 210/211:359 (1992); Kumar, A. et al., J. Am. Chem. Soc. 114:9188 (1992)) have been either proposed or demonstrated, underscoring the importance of materials advances in this area. Of particular significance to interfacial materials and thin films is the ability to grow layered materials where there is good control over the layer thickness and uniformity. Layer-by-layer deposition of films can provide spatial resolution and directionality, and both of these structural properties can be critical to the macroscopic properties of the system. To achieve controlled, layer-by-layer growth requires the development of efficient and robust means of connecting individual layers. Several different techniques have been devised for linking individual molecular layers, including covalent (Netzer, L. et al., J. Am. Chem. Soc. 105:674 (1983); Tillman, A. et al., Langmuir 5:101 (1989); Liu, Y. et al., Angew. Chem. Int. Ed. Engl. 36:2114 (1997); Kohli, P. et al., J. Am. Chem. Soc. 120:11962 (1998)), ionicxe2x80x94covalent (Lee, H. et al., J. Am. Chem. Soc. 110:618 (1988); Lee, H. et al., J. Phys. Chem. 92:2597 (1988); CAD, G. et al., Acc. Chem. Res. 25:420 (1992); Putvinski, T. M. et al., Langmuir 6:1567 (1990); Katz, H. E., et al., Chem. Mater. 3:699 (1991); Yang, H. C. et al., J. Am. Chem. Soc. 115:11855 (1993); Thompson, M. E., Chem. Mater. 6:1168 (1994)), coordination (Bell, C. M. et al., Mater. Chem. Phys. 35:225 (1993)), charge-transfer (Shimazaki, Y. et al., Langmuir 13:1385 (1997); Shimazaki, Y. et al., Langmuir 14:2768 (1998)), hydrogen bonding (Sun, L. et al., Langmuir 8:2101 (1992)) and alternate adsorption of oppositely charged polyelectrolytes. Decher, G. et al., Chem. Macromol. Symp. 46:321 (1991); Decher, G. et al., Bunsen-Ges. Phys. Chem. 95:1430 (1991); Decher, G. et al., Thin Solid Films 210/211:504 (1992). Many of these methods are well suited to the deposition of multilayers of small molecules and can be used for the deposition of polymers under certain circumstances. For several of the linking methods, however, the stability of the resulting structures is limited under conditions of high temperature or solvent exposure. Only the approaches that use covalent or strongly ionic interlayer linking chemistry can withstand thermal and solvent attack.
Polymers containing anionic functional groups can also play an important role in metal reclamation and water purification by chelating metals to remove them from media such as waste water. The most viable chemical techniques for treatment of metal bearing effluents include electrolytic deposition, metallic replacement, ion exchange, chemical reduction and chemical precipitation. While electrolytic deposition, metallic replacement, ion exchange and chemical reduction are all reasonably effective, chemical precipitation is believed to be the most effective method for metal removal from waster water effluents. Two general chemical precipitation methods are known for removing heavy metals from waste waterxe2x80x94hydroxide precipitation and sulfide precipitation. Hydroxide precipitation has limitations, however, due to high solubility and amphoteric properties of metal hydroxides. In addition, the technique is not effective in the presence of chelating agents, which are commonly used in metal finishing operations. Sulfide precipitation is an alternate method which does not have the shortcomings associated with hydroxide precipitation, however three additional problems exist with sulfide precipitation. These are the necessity to control excess sulfide ion, the necessity to control pH to avoid the production of toxic and noxious hydrogen sulfide gas, and the problems associated with the filtration of the very fine metal sulfide particles.
It would therefore be desirable to provide materials that could be used for the synthesis of thin films and chemically modified surfaces. It would also be desirable to provide materials that produce uniform layers. It would further be desirable to provide methods of synthesizing thin films where the thickness of the layers could be controlled. It would also be desirable if the thin films formed from such materials and methods are stable, especially at high temperatures and/or solvent exposure.
It would further be desirable to provide materials that could chelate metals to sequester or recover such metals. It would also be desirable for such materials to be polychelants, increasing their efficiency. It would further be desirable to provide methods of sequestering or recovering metals that are less hazardous than the current chemical precipitation methods.
The present invention provides novel organic copolymers comprising alternating functional groups, wherein one functional group is phosphonate. In one embodiment, the copolymers of the present invention comprise alternating phosphonate and N-substituted succinimide functional groups. In another embodiment, the copolymers are synthesized from maleimide and vinyl ether monomers. In yet another embodiment, the vinyl ether monomer possesses a pendant phosphonate functionality and the maleimide monomer is an N-substituted maleimide.
The present invention also provides methods for producing polymer multilayer structures using the novel alternating copolymers. In one embodiment, multilayer structures are produced by layer-by-layer deposition of the alternating copolymers on a substrate using metal-phosphonate interlayer linking chemistry. The thickness of the layers may be controlled by the size of the substituent of the N-substituted maleimide of the alternating copolymer, wherein the thickness of the layers is proportional to the size of the substituent. The methods provided herein produce uniform layers.
The present invention further provides novel methods for metal chelation and metal reclamation using the novel alternating copolymers. In one embodiment, the anionic phosphonate groups chelate metals. In another embodiment, the alternating copolymer further comprises an acid functionality on the maleimide. Such novel copolymers produce a more efficient chelator.